This project represents an ongoing study of the mechanical, metabolic and electrical abnormalities of the diseased heart. It is concerned primarily with identification of functional defects which characterize or presage myocardial failure and with mechanisms of ventricular arrhythmias in experimental ischemic heart disease. Work is in two general areas: ventricular function and electrophysiology. The former includes: 1) a prospective study of patients with chronic volume overload utilizing cardiac ecohography (and invasive studies) to identify methods of choosing the optimum time for surgical intervention. Ventricular dimensions, systolic performance and volume/mass ratios of the ventricle are being analyzed serially and correlated with hemodynamics and clinical course, 2) studies of ventricular relaxation and compliance in the intact dog heart with special reference to coronary dynamics and loading conditions. The electrophysiologic studies involve computerized measurements of unipolar strength-interval curves and conduction times in experimental acute myocardial ischemia and reperfusion: effect of antiarrhythmic agents; studies of ventricular recovery properties of extrasystoles and an analysis of pacing modalities upon ventricular recovery properties.